Trunked communication systems are known to include a wireless infrastructure and a plurality of communication units, such as mobile or portable two-way radios or mobile data terminals. Some communication systems, such as those used for public safety, also include a dispatch console and a so-called “computer aided dispatch (CAD) system” that includes a display-based terminal to control communications between the communication units. The CAD terminal typically displays categorized tables of information to the terminal user (typically referred to as a “dispatcher” or “dispatch operator”). For example, the CAD terminal may display queues of currently pending incidents and/or a list of communication units that are currently available. In addition, some CAD terminals include an integrated mapping program that enables the CAD terminal to display locations of communication units on a map that represents a geographic area supported by the dispatch system. The locations of the communication units are typically provided to the CAD system on a periodic basis by an automatic vehicle location (AVL) system that is coupled to the CAD system via a dedicated communication link.
In addition to receiving communication unit location information, the CAD system may also receive incident information from a 911 system that is coupled to the CAD system. For example, the map may display the origination point of a 911 telephone call to the dispatcher as an icon on the map. By viewing communication unit location, communication unit status, and incident location on the map, the dispatcher can determine which communication unit users (e.g., policemen, firemen, paramedics, and so forth) would be in the best situation to respond to the incident. As an incident is attended to by users of the communication units, the status of the communication units associated with such users is updated either manually by the dispatcher or automatically by the CAD system responsive to messaging from the wireless infrastructure. In the latter case, the wireless infrastructure receives status updates over a wireless communication channel from the communication units that are participating in the handling of the incident. Changes in communication unit status are typically indicated to the dispatcher by some type of visual change, such as a color change or icon update, to the participating unit's representation on the map.
A map display, with icons representing the incidents and the communication units with their current status, gives a dispatcher a useful tool for evaluating an emergency situation. By using standard graphical user interface (GUI) cursor interaction (e.g., point and click or drag and drop), the dispatcher can manipulate the screen icons to assign units to incidents. Thereafter, the dispatcher may communicate information to the assigned units such as, for example, the incident location and other details. As one may appreciate, such systems place a heavy burden upon the dispatch operator, particularly where events and details are rapidly changing. It is possible that a dispatcher might assign units to an incident that are not in the best position to respond or conversely, fail to assign units that otherwise would wish to respond or at least monitor the event. Perhaps even more problematic is the difficulty in determining the type, extent and timing of information to be provided to the assigned units. The problem is exacerbated when one considers that certain units may wish to change their level of participation as the incident progresses.
For example, consider a police chase scenario involving multiple police cars pursuing a fleeing vehicle. It would be desirable for all of the pursuing police cars to receive real time location and/or route information to determine what they each will do to help stop the wanted vehicle. In most instances, the police chase scenario relies upon the lead car broadcasting cross-street references directly to the other assisting vehicles or to the dispatch center for re-broadcast. The dispatch operator is burdened with determining which of the field units are involved in the event, relaying the cross-street references and team member location information to the team. However, this verbal method is prone to errors and it distracts the lead unit from the primary task of the high-speed chase. In addition, the lead car or assisting cars may not really know what other units are assisting in the chase and where they are. Knowing the total “team” of assisting units and where they are, what routes they have followed and what routes they are planning to follow can help determine a chase strategy.
Even if the team member location could be conveyed correctly from the dispatcher to all participating vehicles, the comprehension of the spatial relations of these vehicle locations to other important and relevant events, temporary and potentially moving objects may be severely impaired if not completely impossible. Such temporal objects could include injured persons, pockets of activities of accidents and violence, etc. On the other hand, the continuous transmission of location information to a remote site where it may be displayed also in non-emergency situations may pose an additional problem of the perceived intrusion of work-place privacy or even a security risk. As one can imagine, the current location methods are very error-prone, untimely, limited both in the completeness of location information to be conveyed and in the desired access control.
Current methods are also are deficient in terms of route information, such as the visualization of the spatial context of traversed trajectories, planned routes of the work-team members and the moving objects related to an event. Route information (e.g., knowing which routes are to be followed, or which routes have already been visited by other responding vehicles) and the timeliness of the route information is also important, particularly in assignments where territorial coverage optimization is needed or desired. Examples of such missions are neighborhood-patrolling, search for persons and/or for objects, public works for snow removal, road inspections, utility readings, delivery drop-off/pick-up routes, on-demand car-pooling, etc. Particularly for larger work groups, up-to-date route information would have been impossible to convey only verbally, especially when the routes are changing based on real-time events. In real life situations, a compounded problem is the need for a real-time, on-going optimization of the set of routes for all group members as a whole, which makes the use of a verbal only communication with no visualization support even less effective.
Accordingly, there is a need for a group location and/or route sharing service whereby participating communication units share location and/or route information for a particular event. It would be desirable for field units themselves, or a third party on behalf of the field units, to subscribe for participation in an event based on the communication units' ability or desire to respond. Advantageously, the subscribing units may comprise a talkgroup or subset of a talkgroup assigned to an event. There is further a need for such a group location and/or route sharing service to provide for different levels of participation and/or service levels for the subscribing units. The service levels may include, for example, an information transmission service level and information reception service level that determine an amount, type, and/or timing of information to be sent or received by particular subscribers. The present invention is directed to addressing or at least partially addressing these needs.